Exhaust Frame Differential Cooling for Gas Turbine Shaft Alignment
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Solution Overview
Problem
Gas turbine engines face issues with temperature differentials leading to 'back bone bending' and rotor to casing misalignment due to high thermal stresses, causing performance decay and potential blade failure.
Innovation Solution
A differential cooling system for the exhaust frame, equipped with temperature sensors and a cooling air metering system, actively blows cooling air through the bearing tunnel and struts to mitigate temperature differentials and maintain shaft alignment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the gas turbine engine operates at increasingly higher temperatures to improve efficiency, then the power output and efficiency are improved, but the thermal stresses cause backbone bending and rotor to casing misalignment
Solution Approach 1:
The patent applies differential cooling to specific localized areas of the exhaust frame - specifically cooling the top portion more than the bottom portion when top-to-bottom temperature differentials are detected. This localized quality change allows the system to maintain overall high operating temperatures for power generation while creating targeted thermal compensation zones that counteract backbone bending and maintain shaft alignment.
Solution Approach 2:
The system dynamically changes thermal parameters by actively controlling cooling air flow rates to different regions of the exhaust frame based on real-time temperature differential measurements. By adjusting the cooling parameter distribution, the system compensates for thermal-induced deformations and maintains shaft alignment stability even at high operating temperatures.
2Stability of the object's composition
If cooling air is blown through the bearing tunnel and exhaust frame components, then the temperature differential is reduced and shaft alignment is maintained, but the system complexity increases
Solution Approach 1:
The cooling air metering system serves multiple functions: it cools the bearing tunnel to maintain shaft alignment, it compensates for backbone bending by creating differential cooling across the exhaust frame, and it can be integrated with existing turbine cooling infrastructure. This multi-functionality reduces the need for separate dedicated systems and justifies the added complexity through consolidated utility.
Solution Approach 2:
The system incorporates temperature sensors that continuously monitor temperature differentials across the exhaust frame and bearing tunnel, feeding this information back to the cooling air metering system. This feedback loop enables automatic adjustment of cooling air distribution to maintain optimal shaft alignment without requiring manual intervention or complex mechanical adjustment mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The system effectively minimizes centerline eccentricity of the shaft, preventing material removal and blade failure, thus maintaining gas turbine performance across various operating conditions.
Implementation Method 1
hot combustion gases generated in one or more combustors generally may flow along a hot gas path extending through a turbine and an exhaust frame... the turbine and the exhaust frame may be subjected to high temperatures resulting from the flow of combustion gases along the hot gas path, which may result in the generation of high thermal stresses in these components
Implementation Method 2
top-to-bottom temperature gradients may develop therein that may lead to 'back bone bending' of the components therein
Data Source
AI summary
The present application provides an exhaust frame differential cooling system of a gas turbine engine to mitigate a temperature differential along a compressor and/or a turbine to minimize centerline eccentricity of a shaft. The exhaust frame differential cooling system may include a number of compressor temperature sensors positioned about the compressor and/or a number of turbine temperature sensors positioned about the turbine, an exhaust frame including an inner barrel with a bearing tunnel for the shaft, an outer barrel, and a number of struts extending from the inner barrel to the outer barrel, a blower, and a cooling air metering system that provides cooling air from the blower to the bearing tunnel and through the inner barrel, the struts, and the outer barrel in response to the temperature differential being determined along the compressor and/or the turbine.